Successful communication of real-time voice or video calls over a data network requires a minimum bandwidth, and latency, in both directions such that the data network is capable of transmitting the voice and/or video data without undue delay, or interruption. If sufficient bandwidth is not available, call quality can easily become distorted to the point of being unintelligible. It is often the case that this bandwidth insufficiency occurs in one direction only, a condition known as asymmetric bandwidth starvation, either because of varying network loads, or because the local access point has been engineered to provide asymmetric connections. This is often done deliberately as a cost saving, to take advantage of the reality that the network load of many network-based applications is in fact asymmetrical. For example, web pages have a very small uplink requirement (e.g., the page reference to URL) in proportion to their download requirement (e.g., the web page itself).
In the presence of an asymmetric network connection, the user of a real-time voice over data application (e.g., Voice over Internet Protocol, or VOIP) application) may well experience perfect audio in one direction, and unintelligible audio in the other. Similarly, a video application may receive and present video smoothly, but send video such that is choppy when played at the remote device. However, there is still bandwidth available to transmit the audio or video, just not enough of it to perform this in real time as required for the voice or video over data application.